You can build some Hummingbirds and put them on area patrolling over you base. In this way they'll fly continuously over your base protecting you from enemy fireflies, fighters or bombers.

Fighters are sometimes used to replace scouts in their intelligence function due to their superior survivability. They have a better chance of coming back alive from an enemy base, however they have a less vision radius.

Fighters are usually used in groups. Individual fighters aren't very effective, particularly because it takes several passes to destroy enemy air units.